Field of the Invention
The present invention relates to mobile communication.
Related Art
3rd generation partnership project (3GPP) long term evolution (LTE) evolved from a universal mobile telecommunications system (UMTS) is introduced as the 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a downlink, and uses single carrier-frequency division multiple access (SC-FDMA) in an uplink. The 3GPP LTE employs multiple input multiple output (MIMO) having up to four antennas. In recent years, there is an ongoing discussion on 3GPP LTE-advanced (LTE-A) evolved from the 3GPP LTE.
As disclosed in 3GPP TS 36.211 V10.4.0 (2011-12) “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 10)”, a physical channel of LTE may be classified into a downlink channel, i.e., a PDSCH (Physical Downlink Shared Channel) and a PDCCH (Physical Downlink Control Channel), and an uplink channel, i.e., a PUSCH (Physical Uplink Shared Channel) and a PUCCH (Physical Uplink Control Channel).
Meanwhile, an environment in which a plurality of small-scale cells (or small cells) are implemented or a plurality of small cells and macro cells are used together may be considered or implemented in recent years.
In this case, a small cell may be used as a primary cell (Pcell) of a specific user equipment (UE), and the small cell may be used only as a secondary cell (Scell).
In addition, recently, in order for the UE to be able to more effectively discover densely located small cells, it is considered to generate and transmit a new discovery signal, i.e., a discovery signal (DS) and a discovery reference signal (DRS), in addition to the existing primary synchronization signal (PSS)/secondary synchronization signal (SSS).
That is, in the small cell environment, it may be necessary to introduce a cell search procedure or cell discovery procedure using the discovery signal (DS or DRS).
However, the introduction of the discovery signal may cause a problem in that a base station must provide a great amount of additional configuration information.